I agree, you are right, of course. I was just pointing out that it is (sort of) ok to say "Tomorrow it is Wednesday" - and DL usually lets you off for only missing punctuation (even when it is important).
For people who think that punctuation is unnecessary: A comma can save someone's life, there is a BIG difference between "Let's eat grandma" and "Let's eat, grandma".
To elaborate on what Santi_Minstrel said, I'll add that I think he was referring to the fact that you added a pronoun subject (that is, "it") after the noun subject, which is the English noun "tomorrow."
Although the Spanish null subject pronoun "it" is understood to be part of the syntax and grammar of this Spanish sentence, it is unnecessary and incorrect syntax to use both a noun subject and a pronoun subject in a translation into English.
The word semana comes from Latin septimana [7 days]. The names of the seven days come from 7 objects which the Ancient Mesopotamian saw move through the sky. Romans took this to name their days:
- Luna [Moon] (Lunes, from Lunae dies),
- Marte [Mars] (Martes, from Martis dies),
- Mercurio [Mercury] (Miércoles, from Mercurii dies),
- Júpiter [Jupiter] (Jueves, from Iovis dies),
- Venus [Venus] (Viernes, from Veneris dies),
- Saturno [Saturn] (Sábado, from Saturni dies first, then changed due to hebrew influence),
- Sol [Sun] (Domingo, from Solis dies first, then changed due to Christian influence)
Note that Dominus is Lord in latin, Domingo really comes from dominica (Lord's day, day of rest for Christians, based on Genesis where it appears the seventh), and Sábado comes from Sabat (day of rest for Jews, God rested that day and the Christian week still had not been set at that moment, therefore the Day of the Sun was the first day of the week and the Sabat, the seventh).
"El [weekday]" most often translates to "on [weekday]" in English. So since you can say "The game is on Wednesday", the Spanish sentence should be "El partido es el miércoles". But you can't say "Tomorrow is on Wednesday", so it's only "Mañana es miércoles."
Or differently expressed, both mañana and miércoles are days, so you can equate them without an article. On the other hand, "el partido" is not a day, but an event. You can only place it within a day, so you need the article.
http://www.howto.gov/web-content/multilingual/spanish-guide/capitalization for more specific times that you would use capitalization in Spanish. It seems a lot of rules are different from language to language. >.>